The Breast Cancer Surveillance Consortium (BCSC) has been in existence for many years and has collected extensive data on breast cancer screening in the US. This resource has been of great use in answering many important questions about mammography use, including effectiveness, false positive rates, diagnostic evaluation and method of detection. It is advantageous to the breast cancer research community to maintain this resources, as many questions still remain about breast cancer screening with mammography. This contract will provide for use of the BCSC database, including preparation of data sets for breast cancer researchers, and scientific and statistical expertise for those researchers who wish to use the database. The contract will also provide for establishment of a web-based data query tool, one that will allow researchers to independently and quickly access BCSC data. The public health impact of this contract will be large, as findings from the research that uses the BCSC data will directly impact screening practices in the US and abroad.